1. Technical Field of the Invention
The present invention relates to starters and, more particularly, to a starter the type in which a minion moving body, held in helical spline engagement with an output shaft at an outer circumferential periphery thereof, which is pushed toward an engine (in a direction opposite to a motor) to cause a pinion gear to be brought into meshing engagement with a ring gear.
2. Description of the Related Art
In the related art, there has been known a starter, which is disclosed in Japanese Patent Application Publication No. 2006-207573 (Patent Publication 1).
With such a structure shown in FIG. 4, the starter device is of the type including a housing 100 having a nose portion 101 protruding toward an engine and internally formed with an opening portion 102, and a motor 110 fixedly mounted on the housing 100. The motor 110 has an armature 111 provided with an armature shaft 111a, to which an output shaft 150 is connected via a speed reduction gear unit 120 and a clutch 130. The output shaft 150 has one axial end, placed in opposition to the motor 110, which is rotatably supported with the nose portion 101 at a distal end thereof via a bearing 140. The output shaft 150 has an outer circumferential periphery formed with a spline 102, to which a spline tube 160 is held in spline coupling engagement. The spline tube 160 has one axial end integrally formed with a pinion gear 170. When an electromagnetic switch 180 is energized, a shift lever 190 is drivably actuated to push the spline tube 160 toward the engine (rightward as viewed in FIG. 4). This causes the pinion gear 170 to be brought into meshing engagement with the ring gear 200 of the engine.
With the starter of such a related art, no issue occurs in normal use. However, under a situation where a vehicle runs on, for instance, a punishing road with the starter being used under an extremely adverse condition, there occurs a risk in which foreign materials such as grit and dust or water droplets, etc., collected by the ring gear 200 intrude inside of the starter through the opening portion 102 of the housing 100. Moisture, containing grit and dust or the like, causes defective sliding engagements to occur when intruded into sliding sections such as the speed reduction gear unit 12 and the clutch 130, etc.
With the starter of such a related art described above, however, no expedient measure has been undertaken for suppressing the intrusion of grit and dust or water droplets with a concern for degraded performance and defective operation of the starter resulting from defective sliding engagements of as the speed reduction gear unit 12 and the clutch 130 or rusting results of internal component parts.